CoffeeScript is syntactic sugar for JavaScript. TypeScript is optional static type checking for JavaScript. Dart is optional static type checking plus various incompatible semantic cleanups and a standard module system for JavaScript.

TypeScript is definitely closer to Dart than CoffeeScript, but it doesn't go so far as to break JavaScript compatibility like Dart does. CoffeeScript-like syntactic sugar could be implemented as a pre-compiler for either language. LawnDart, if you will.